Computers and their associated bus architecture and protocol establish a framework upon which other items like integrated circuits and add-on cards (collectively called peripherals) are based. The bus and a bus controller provide a means for the computer to communicate with peripherals coupled to the bus. The functional operation and the bus cycle length used (herein called cycle length) when the computer accesses these peripherals is limited by parameters established by the particular bus and used by the bus controller. Some of the peripherals coupled to the bus are able to operate using shorter bus cycle lengths. Other peripherals require a longer cycle length. One such computer is the IBM/AT personal computer sold by IBM Corp. The bus architecture used by the IBM/AT computer is called the ISA bus.
One way for these computer systems to improve performance is to shorten all the bus cycles on the bus to take advantage of the greater bus bandwidth. However, peripherals that do not support the shorter bus cycles would be incompatible and therefore inoperable with the computer system. One way to avoid this incompatibility is to support two separate buses, one bus that executes shorter bus cycles, another that executes longer bus cycles. This solution, however requires additional and redundant hardware, thereby increasing the overall cost of the system.
A single bus controller is needed which supports different bus cycle lengths, yet maintains compatibility with all peripherals without the need for additional and redundant hardware.